This application relates to ultrasonic imaging devices such as ultrasonic imaging catheters and to methods for fabricating these devices.
Ultrasonic imaging techniques are often used to gather images during medical procedures. For example, ultrasonic imaging catheters may be used to gather images from within the body lumens of a patient during the diagnosis and treatment of medical conditions. During percutaneous transluminal coronary angioplasty procedures, images may be acquired from within the blood vessels of a cardiac patient to help a physician to accurately place an expandable balloon.
In a typical ultrasound imaging catheter configuration, a piezoelectric ultrasound transducer array near the distal end of the catheter may be used to generate high-frequency acoustic signals that radiate towards the image target (e.g., a patient""s blood vessel). The transducer array also gathers corresponding reflected acoustic signals. Image processing techniques are used to convert the reflected acoustic signals into images for the physician.
When the expandable balloon and ultrasound transducer are part of the same catheter, size and placement considerations have generally dictated that the ultrasound transducer be located at a more proximal location than the balloon. With this arrangement, the ultrasound transducer is offset from the distal tip of the catheter by at least the length of the balloon. The images from the ultrasound transducer therefore cover a portion of the patient""s blood vessel that is offset from the distal tip of the catheter being advanced into the patient""s blood vessel by the physician. It would be desirable to reduce or eliminate this offset to improve the physician""s view of the patient""s blood vessel in the vicinity of the distal catheter tip. Also, in many cases it is desirable to cross a lesion with an imaging device prior to crossing the lesion with a therapeutic device so that the treatment site may be visualized prior to crossing.
It is an object of the present invention to provide ultrasonic imaging catheters in which the ultrasound transducer is located distally and an expandable balloon is located proximally on the distal end of the catheter.
It is also an object of the present invention to provide ultrasonic imaging catheters with distally-located ultrasound transducers having small crossing profiles.
It is another object of the present invention to provide improved techniques for fabricating ultrasound imaging catheters.
These and other objects of the invention are accomplished in accordance with the principles of the invention by providing ultrasonic imaging catheters with ultrasound transducers at their tips and by providing modular and non-modular methods for fabricating these catheters.
An imaging catheter constructed in accordance with the invention may have an ultrasound sensor at its distal tip. The imaging catheter may be used in an ultrasound imaging system to gather ultrasound images for a physician or other user.
The sensor may have a transducer array formed from piezoelectric elements. The piezoelectric elements may be mounted on a flexible substrate. The flexible substrate may include conductive lines and integrated circuits for handling the signals conveyed to and from each of the transducer array elements. The flexible substrate and mounted components may be referred to as a xe2x80x9cflex circuit.xe2x80x9d The flex circuit may be wrapped around a guide wire lumen to form an ultrasound transducer assembly with an integral guide wire lumen.
The ultrasound transducer assembly may be attached to the distal tip of the catheter. This transducer location provides good diagnostic imaging capabilities for the user of the ultrasound imaging system. An expandable balloon (e.g., a balloon suitable for expanding a patient""s blood vessels during angioplasty or for deploying a stent) may be located on the proximal side of the ultrasound transducer. This allows the imaging catheter to be used as a treatment device.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.